In many electrical fields, arcing, i.e. electrical discharging, can occur. Some arcing can be a normal part of the operation, while some arcing is undesired and can even be dangerous.
As a first example, in power transformers, on-load tap changers (OLTC) are used to change tapping connections of transformer windings while the transformer is energized. Some arcing will occur, and it is desired to keep such arcing inside vacuum containers, rather than e.g. arcing in transformer oil. Arcing in oil can create wear on contacts and reduces the quality of the oil. It is therefore desired to be able to discriminate between normal arcing inside the vacuum container and undesired arcing outside the vacuum container. Avoiding arcing in oil allows the use of less expensive material in the contacts and increases the time between oil changes, thus allowing for longer maintenance intervals.
As a second example, in electrical motors, both normal and undesired arcing may occur, and it is desirable to discriminate between these two.
Consequently, there is a need to detect and discriminate between normal arcs and undesired arcs.